The invention relates to the technical field of grinding machines, in particular to an external-circle grinding machine. The external-circle grinding machine comprises a machine body, a barreling motor, a mounting plate, a fan, a connector, a dust storage box, a filtering net, a three-way pipe, a cover, a U-shaped limiting piece, a threaded column, a cleaning barrel, a column body, a transverse plate, a water pump, a water tank, a bearing, an arc-shaped plate, first cleaning cotton, second cleaning cotton, a dust outlet joint and a grinding wheel. According to the external-circle grinding machine, under the action of the fan of a dust suction mechanism, grinding dust can be pumped into the dust storage box, under the action of the filtering net inside the dust storage box, the grinding dust is stored in the dust storage box, collection of the grinding dust is facilitated, the condition that the grinding dust drifts around can be avoided conveniently, the quality of the working environment can be improved, when a columnar piece is rounded and then passes through the cleaning barrel of a cleaning mechanism, under the action of the first cleaning cotton inside the cleaning barrel andthe dust outlet joint, dust on the outer surface of the columnar piece is cleaned, cleaning of the columnar piece after rounding is facilitated, and the cleanliness of the columnar piece after rounding can be improved conveniently.